Honestly, why can't I just keep this old Box Springs and just buy a new mattress?

That may seem like a clever thing to do, since to the uneducated observer the Box Springs may be all but worthless and certainly not a piece worthy of replacing. But buyers beware…this is a mistake that could cost you in many ways! You will find very few sources that will encourage such a move and a plethora that will warn you against it!